Blasting with liquid oxygen explosives with the aid of captive balloons



United States Patent U.S. Cl. 10223 1 Claim ABSTRACT OF THE DISCLOSURE A captive balloon carrying oxygen-rich liquid air and liquid methane separately is moored over blast holes. Remote control means mixes the liquids and dumps the resulting explosive in the blast holes. Then the balloon is rapidly drawn away from over the blast holes by a cable and the explosive is set off.

This Patent is a continuation-in-part of my patent application Ser. No. 708,351, filed Feb. 26, 1968 entitled Captive Lighter-Than-Air Craft for Supporting Above Ground Excavating Equipment.

For .summary reread the abstract above. In large diameter blast holes I prefer to line the blast holes first with about 0.5 inch of asphalt and then with an aluminum metal liner.

This invention may be used to blast rock into small pieces so that it can be moved by dragline excavators or power shovels. However its most advantageous use is where suflicient explosive is used not only to break the rock up but to move the rock out of a trench or ditch that is formed.

In this way the expense of moving the blasted rock by draglines, etc., is eliminated but much more explosive is required. This invention allows the completely safe and cheap placement of very cheap but powerful explosives.

By far the cheapest but yet powerful explosive is a mixture of liquid oxygen and liquid methane plus varying amounts of liquid nitrogen. However the mixture is very dangerous and difficult to handle by prior methods. The mixture has the disadvantage that the temperature of the surrounding rock warms up the liquid mixture and the mixture boils off. The time required before the mixture starts boiling may be deferred for several minutes, or even more in large diameter blast holes, by cooling the mixture 20 Fahrenheit or more below its boiling point. However this is not time enough to fill a considerable number of blast holes with the liquid mixture and for workers to get away. It is to be noted that explosives are more efficient per pound if as large as possible weight of explosive is set off at one time.

It may be thought that insulated above ground containers might be provided to store the liquid oxygen, or air, and the liquid methane separately. These would be filled and then with the workers at a safe distance away and by remote signalling the liquids would be mixed and the blast holes would be filled. This would be a completely safe and satisfactory way to use liquid oxygenliquid methane explosives except for the fact that the storage vessels, piping and valves would be lost with each batch of explosive set off and the cost of the lost equipment is to high to bear.

Now I propose to carry the liquid oxygen, or air, and the liquid methane separately to the blast holes by a captive balloon. That is the weight would be carried by the balloon while a truck would pull the balloon along at the end of a cable. However the liquid methane and the oxygen-rich liquid air may be brought separately to the blast holes by any means. Then when the balloon was over the blast holes the pipe and valves for mixing the two liquids would be aranged so the blast holes could be filled on remote signalling and then on remote signalling the balloon would lift the mixing and filling equipment away and the ballon would be drawn rapidly (at perhaps miles per hour) by the use of a long cable that would be perhaps a half mile long. Then with a total time of less than two minutes for the liquid oxygen-liquid methane explosive in the blast hole, the explosive would be set otf.

The arrangement of the pipe and mixing equipment will be obvious to any chemical engineer as those in charge of high explosives and their uses normally are. Since the two liquids to be mixed have low viscosity the flow of the combined streams of liquid methane and liquid oxygen (containing varying amounts of liquid nitrogen) through a pipe at least 50 diameters long under turbulent conditions will mix the two streams very well. (See Chemical Engineers Handbook by Perry, 3rd ed., 1950, McGraw-Hill, New York City, p. 1216, first complete paragraph.) As for controlling the individual flows of the two liquids to be mixed to the mixer very simple equipment may be used. However the best costs little more and control of the ratio of the two liquids mixed with recording of the rates is illustrated in the same reference just above cited, see p. 1333, second column starting with first complete paragraph and finishing on the next page. The mixing and the piping system can easily be designed to give predetermined flow rates of the mixed explosive to the blast holes. As shown in the reference the control valves may be operated by compressed air (of which so little is required that it can be stored in a tank) or by a battery.

The remote control of apparatus in the handling of explosives is old and methods such as shown by G. S. De Montfort in U.S. Patent 3,086,465 may be used to control the mixing of the two liquids and the release of ballast so that the balloon will rise and can be pulled away by a cable.

While it is preferred to carry the two liquids to make the explosive to the blast site by balloon obviously they may be brought to the blast site by other means. However in all cases the containers for the two liquids and the mixing equipment are caried away from the blast site by captive balloon after the blast holes are filled with explosive and before the explosive is set off.

I have found that the cost of the balloon is a very small item in this type of blasting. A 400 foot diameter balloon will carry over 400 tons of explosive. Because of the cheapness of the explosive used the total cost for blasting will be reduced by over if blast holes over 15 inches diameter are used.

With unlined blast holes there is danger of cracking the rock around the blast holes and having some of the explosive liquid drain away. Therefore I usually prefer to line the blast holes. I prefer to first line the blast holes with 0.5 inch of asphalt or high melting residual fuel oil which is cheap. This is done by standard pipe lining equipment. The lining apparatus travels like a mole through a pipe. Asphalt is a good insulator. I prefer to add chopped glass fiber to the molten asphalt before applying to prevent cracking of the hardened asphalt. This lining by itself can be used. However I prefer, and particularly prefer for blast holes over 15 inches diameter, to also use an aluminum metal liner inside of this. This metal liner is made of aluminum 2-6 gage sheet metal resistance welded to make a liquid tight container.

If the holes are horizontal or slanting, there is no danger of liquid explosive falling the entire distance of the blast hole and possibly igniting by frictionally produced static electricity. For vertical blast holes I prefer to provide a tube for the liquid explosive to flow down with the tube full at all times. The flow is started in the tube by allowing some liquid oxygen, or air, that does not contain the liquid methane to How down first. This filling tube is made by resistance welding together a tube out of 26 gage aluminum sheet metal.

As said previously the cost of the balloon is a minor item when compared to the tons of explosive it can carry in a year. The balloon can be made out of polyethylene sheet held within a network of polypropylene rope.

The captive balloon used can carry other things besides the explosives. A captive balloon can carry the big drills for drilling the blast holes. In this way a large number of blast holes can be drilled at a time with one crew of men. The practice of mounting just two drills a hundred feet high on a truck requires very good roads to be built to the blasting site to keep the trucks from tilting over. A captive balloon can carry perhaps 20 drills at a time and there is no need for good road building to the blasting site.

I normally prefer to use liquid air containing about 45% liquid oxygen for my source of oxygen. This is a very cheap form of liquid oxygen. It has the advantage that when mixed with the exact amount of liquid methane to burn up the oxygen that the mixture does not produce explosive vapors when it boils. However boiling is very undesirable since it may produce static electricity that can set off the liquid mixture present.

I define a captive balloon as a spherical bag holding a lifting gas that is preferably hydrogen gas. The balloons movements are controlled from the ground by cable or cables tied to the balloon.

In summarizing my invention I may say that I have disclosed a completely safe and cheap method for using the very cheap but powerful liquid oxygen, or air, plus liquid methane explosives.

I claim:

1. A method of blasting using liquid oxygen and liquid methane in blast holes wherein all personnel can be located at relatively safe distances from the blast holes which comprises: mooring a captive ballon near the blast holes, bringing containers carrying separately liquid oxygen and liquid methane to the blast holes, actuating by remote control mixing equipment to mix the liquid oxygen and liquid methane and to pour the resulting explosive into the blast holes, utilizing the captive balloon to carry the emptied containers for the liquid oxygen and liquid methane and the mixing equipment safely away from the blast holes, and then setting off the explosive.

References Cited UNITED STATES PATENTS 37,771 2/1863 Perley 891.5 442,678 12/1890 Hartley 102-23 603,182 4/1898 French 891.5 X 603,689 5/1898 Hill 891.5

1,508,185 9/1924 Haynes 1491 2,886,424 5/1959 Hyslop 10223 X 3,035,519 5/1962 Barlow 102-23 3,086,465 4/1963 Montfort 102 22 VERLIN R. PENDEGRASS, Primary Examiner U.S. Cl. X.R. 8620 

